A lot of the game before you escape the testing track, minus maybe the point you are told about momentum jumps, feel like one big tutorial without even realizing you're in one. It's done very well.

I'm here to say Portal as well, specifically because, once you really look for it, you realise that about 90% of the game is tutorial. Like, seriously, basically everything leading up to "The cake is a lie" is teaching you the skills you need for the final sequence. It's a massive tutorial followed by one level of actual game, and it's beautiful, precisely because you don't even notice that the tutorial hasn't ended.

Portal 2 imo. Stephen Marchant makes everything better

When I played through Portal in dev commentary mode, I was surprised at the time to realize they're basically trying to teach you things through the whole game (or at least heavily signpost). Made me realize a lot about game design, and design in general.